In recent years, engineering plastic materials have been used in increasingly diversified and sophisticated applications. In applications which require the blending of two or more non-compatible polymers, it can be effective to use a compatibilizer, such as a block or graft copolymer containing a segment having an affinity for each polymer to be blended, in order to obtain a formed article in which one polymer is in a very finely dispersed state and the continuous and dispersed phases are tenaciously bonded with each other. One important method for synthesizing such a compatibilizer would be to react functional group-containing polymers reactive with each other which could thereby bond to the non-compatible polymers. Thus, there is a strong desire to develop a resin which contains a reactive functional group.
It has been proposed to incorporate various functional groups into poly(phenylene ether)s by using a terminal phenolic hydroxyl group as a reaction site. For example, known modified poly(phenylene ether)s include a terminal-carboxylic anhydride-modified poly(phenylene ether) as disclosed in JP-A-63-199754 or JP-W-62-500456, a terminal-alcoholic hydroxyl-modified poly(phenylene ether) as disclosed in U.S. Pat. No. 4,746,708, and a terminal-glycidyl-modified poly(phenylene ether) as disclosed in U.S. Pat. No. 4,732,937. (The terms "JP-A" and "JP-W" as used herein mean an "unexamined published Japanese patent application" and "an unexamined published international application", respectively.) However, since the number of reaction sites and the number of functional groups per molecule of poly(phenylene ether) are at most one, none of these known polymers are acceptable for use as a compatibilizer.
On the other hand, U.S. Pat. No. 5,019,631 discloses a poly(phenylene ether) having a large number of functional groups per polymer chain. This poly(phenylene ether) is an amorphous modified poly(2,6-di-methyl-p-oxyphenylene), having a glass transition temperature of from 180.degree. to 220.degree. C., in which from 10 to 60%, on the average, of the polymer structural units comprise: ##STR3##
The above polymer is obtained by a process comprising: (a) metalating poly(2,6-dimethyl-p-oxyphenylene) with an alkaline metal in an inert solvent at a tempertaure from -30.degree. to 80.degree. C. for about 1 minute to 4 hours where the alkaline metal is selected from the group consisting of an alkaline metal C.sub.1 -C.sub.12 -alkyl, an alkaline metal hydride, and an alkaline metal amide, with the molar ratio of the metalating agent to the poly(2,6-dimethyl-p-oxyphenylene) being from 0.1:1 to 1:1; (b) reacting the metalated poly(2,6-dimethyl-p-oxyphenylene) with ethylene oxide, in an amount at least equal to the amount of the alkaline metal in step (a), in an inert organic solvent at a temperature of from -30.degree. to 80.degree. C. for about 5 minutes to 2 hours to form a modified poly(2,6-dimethyl-p-oxyphenylene); and (c) recovering the modified poly(2,6-dimethyl-p-oxyphenylene).
However, the above process has several disadvantages due to the high reactivities of the metalating agent used and the metalated poly(phenylene ether) formed during the process. Both can readily react with water, carbon dioxide, and other substances present in the reaction system. This reduces the activity of the metalating agent and causes its selectivity to be as low as 50% or less. Additionally, the recovery of the modified polymer is only about 70%. It is also difficult to control the amount of alcoholic hydroxyl groups incorporated into the polymer. Thus, from the standpoint of commercial production of the modified polymer, the above process has various problems which need to be overcome.
An effective method for incorporating a functional group is to copolymerize 2,6-dimethylphenol with a monomer compound having a functional group. However, in the known copolymers which can be included in the class of poly(phenylene ether)s the substituents on benzene rings in the backbone have been limited to alkyl groups, alkenyl groups, aromatic groups, halogens, and alkoxy groups.
Therefore, a process is needed which can provide a poly(phenylene ether) having a predetermined level of a reactive functional group.